1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to a semiconductor device equipped with an electric fuse. The present invention further relates to a method of manufacturing such semiconductor device.
2. Background Art
In a process of manufacturing a semiconductor device such as a memory device, various tests are performed in a wafer stage. In one test, a metal interconnection is cut by radiation of a laser beam from the outside onto a predetermined area on the interconnection. In other test, a voltage is applied to a specific interlayer film in a semiconductor chip, to thereby electrically break the interlayer dielectric film and induce a short circuit in the interlayer dielectric film to act as an electric fuse. Through such tests, a failed wafer is repaired or a wafer is subjected to voltage control.
However, in a case where a metal interconnection is exposed to a lasers, the wafer must be in a state such that the interconnection can be subjected to laser irradiation. Therefore, laser irradiation of an interconnection can be employed only in a wafer stage. After the wafer has been diced into semiconductor chips, laser irradiation cannot be performed.
In the course of laser irradiation, damage is imparted to a circuit located around a target position on the wafer. Hence, a circuit cannot be located near or below a fuse section, thus rendering chip layout difficult.
In the event of a failure arising in the radiation position for any reason, very serious damage such as destruction of a peripheral circuit occurs, thus making repair of a semiconductor device impossible.
Application of a voltage to cause an interlayer film to act as an electric fuse can be effected even after a semiconductor chip has been assembled. Further, application of a voltage inflicts less damage on surroundings of the electric fuse than does laser irradiation. Hence, circuits can be fabricated in positions above and below the electric fuse, thereby advantageously facilitating chip layout. However, a limited voltage can be applied to the inside of the semiconductor chip. In order to destroy an interlayer film thoroughly, the area of an electric fuse to be subjected to application of a voltage must be increased, thus hindering miniaturization of a semiconductor chip.
The present invention has been conceived to solve the above-mentioned drawback of the background art and is aimed at providing a semiconductor device whose electric fuse is fabricated with a very thin film so as to enable performance of electric fuse trimming by means of application of a voltage, which trimming yields many advantages, as well as providing a manufacturing method which enables fabrication of an electric fuse or a capacitor within a narrow area by utilization of a transistor trench isolation LOCOS manufacturing process.
In one aspect of the present invention, a semiconductor device comprises at least an active region formed in the semiconductor substrate separated by a plurality of isolation regions. A surface insulating film is formed on a surface of the active region. A conductive film is formed on the surface insulating film. The surface insulating film is formed relatively thin to be broken down and to work as an electric fuse.
In another aspect, the semiconductor device comprises a plurality of surface insulating films formed on a surface of the active region of the semiconductor substrate, and the surface insulating films are formed at different thicknesses. A plurality of conductive films are formed on each of the surface insulating films. Then, one of the surface insulating films having smaller thickness is caused to break down and to work as an electric fuse.
In another aspect, a semiconductor device comprises at least an active region formed in the semiconductor substrate separated by a plurality of isolation regions. At least a trench is formed in the active region. A surface insulating film is formed along a surface of the trench. A conductive film is formed on the surface insulating film. The surface insulating film is formed relatively thin to be broken down for forming an electric fuse. Alternatively, the surface insulating film is formed relatively thin to work as a dielectric film for forming a capacitor.
Other and further objects, features and advantages of the invention will appear more fully from the following description.